214 MESSRS, HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 
runs up the inner surface of the buccal lip, tapering away to nothing near the top. 
One edge of this membrane is attached to the buccal lip along the inner margin of 
the collar, the other is free, projecting into the aperture of the mouth. These rudi- 
mentary jaws and the prehensile collar are doubtless formed from the mucous mem- 
brane of the mouth, but we have not seen evidence to prove that they are, together 
or separately, the homologous parts or part to the horny jaws of EoUs, but they seem 
to be engaged in the same function, that of prehension. 
The oesophagus in our typical species* comes from the upper posterior part of the 
buccal mass, is somewhat dilated at first, and then pretty uniform in diameter, 
exceeds the stomach in length, is rather delicate in texture, and its interior is longi- 
tudinally plicated. It runs straight backwards, and opens freely into the posterior 
end of the stomach at the under part, and rather at the right side directly in advance 
of the great hepatic duct. 
The Salivary Glands are a pair of long delicate tubes tapering backwards, where 
they lie against the liver, and open into the mouth on each side at the coming oflT of 
the oesophagus. 
The Stomach is a large ovate membranous bag lying on the left side of the bodj*, 
with its posterior end resting in a funnel-shaped depression in the anterior face of the 
liver. The great duct from the liver-j- opens into this posterior or cardiac end of the 
stomach so widely, that it is difficult to determine the line of demarcation between 
them. This duct, at its union with the stomach, lies above the cardia or entrance of 
the (Bsophagus, which is rather to the right ; it lies also above the opening of a small 
duct from the pancreas, which is situated somewhat towards the left side. At the 
pyloric end, which is anterior in position, the stomach becomes rapidly constricted 
and converted into the intestine, which appears to come off from the under part, 
bends upwards to the right side, and then backwards, running along the right side 
of the stomach between it and the genitalia, inclining gradually towards the right; it 
then passes under the heart and right side of the pericardium, winds round and 
under the right side of the posterior end of the liver, and lastly, ascends behind the 
end of the liver to terminate at a projecting tubular anus in the centre of the 
branchial circle. The internal surface of the stomach is more or less closely and 
finely corrugated ; the rugse are most strongly marked at the upper posterior part of 
the organ in front of the hepatic duct. 
The Intestine, which is of smaller diameter than the (ssophagus, but pretty uniform 
in calibre throughout, has its internal surface longitudinally laminated. 
The Pancreas\ is a somewhat elliptical pouch lying below and at the left side of 
the stomach. Its interior is divided by numerous projecting transverse folds of the 
lining membrane, strongly resembling valvulee conniventes, and usually contains a 
dark brown matter. It opens very freely into the stomach. '\^"e have not examined 
microscopically the muscular coat of the alimentary canal, but on the external sur- 
face of the stomach and pancreas, after the aorta has been injected, can readily be 
* Plate XII. fig. 1. t Plate XIII. fig. 13. t Plate XVII. fig. 5. 
